President Trump told media here that "it is a situation that we will handle".
US Defense Secretary James Mattis said that the North Korea missile fire was the regime's "highest yet and poses global threat".
However, while addressing the media, the Pentagon earlier said that the Intercontinental Ballistic Missile (ICBM) fired by North Korea was non-threatening to the United States, its territories or allies.
White House spokesperson Sarah Sanders said the President was informed on the situation in North Korea while the missile was still in the air.
Sanders tweeted: "President Donald Trump was briefed, while the missile was still in the air, on the situation in North Korea."
The US President was in a meeting with Senate Republicans on Capitol Hill at the time of the missile fire.
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North Korea fired the ICBM in the direction of the Sea of Japan, a first by the country since September 15.
The missile travelled about 1000 km before splashing into the Sea of Japan, said the Pentagon.
"We are in the process of assessing the situation and will provide additional details when available," Pentagon spokesperson Colonel Robert Manning told reporters.
The missile firing comes a week after United States President Donald Trump said that North Korea falls under the list of countries that backs terrorism.
South Korea Military's Joint Chiefs of Staff told the local media about the missile firing early on Wednesday.
The missile "flew eastward from the vicinity of Pyongyang" toward the Sea of Japan, South Korean military officials said.
Japan's Prime Minister's Office said: "North Korea launched a missile that has the possibility of arriving in the exclusive economic zone (EEZ) of our country."
A local media quoted Itsunori Onodera, Defense Minister of Japan, as saying: "North Korea apparently fired an
intercontinental ballistic missile at a steep angle known as a 'lofted trajectory'."
On September 15, North Korea fired an intermediate-range missile, which flew over Hokkaido Island in Japan before and swashed into the Pacific Ocean.
"South Korean unification minister Cho Myoung-gyon told foreign correspondents in Seoul on Tuesday that North Korea is on the verge of achieving full nuclear capability with an intercontinental ballistic missile that could carry a nuclear warhead," Fox news quoted the local media.